Do you see the drive in the device manager? If so it maybe needs to be partitioned and / or formatted. Use Win10 disk management to do that. Be careful, don't wreck your system drives in the process :-)
If the device does not show in the device manager in Win10 it might be disabled in the BIOS. Shutdown, reboot, enter the BIOS and look under Advanced - Devices - SATA. Make sure the SATA chipset is enabled. Choose AHCI and not RAID as mode as I recall (not sure!) you can't have the Samsung NVMe drive in RAID with a SATA drive. Make sure the SATA port is enabled. If everything is fine you should see the Crucial drive mentioned there. At least this is the case in my NUC6i5SYH, albeit with a Crucial MX200.
Hi Paul -
The NUC6i5SYH did not recognize the Crucial M500 SSD via Intel visual BIOS or Win10 Device Manager. I powered down the NUC6i5SYH, removed the Crucial M500 SSD from the cradle and performed a "quick format" via Win 10 file manager using a USB to SATA cable. I then rebooted the NUC6i5SYH, launched the Intel Visual BIOS, and confirmed the Crucial M500 SSD was recognized [it was] and the appropriate settings [SATA chipset, AHCI enabled, Legacy & UEFI boot options enabled] were enabled [they were] as you and Mike C suggested. The only change I had to make via Intel Visual BIOS was under the Boot Priority tab. I noticed the Crucial M500 SSD was placed ahead of the already installed SAMSUNG 950 PRO M.2 SSD in the Legacy Boot Drive Order. I moved the SAMSUNG 950 PRO M.2 SSD to the top of the Boot Drive order. After changing the boot order I was successfully able to boot up the NUC6i5SYH and view both the SAMSUNG and CRUCIAL SSD drives without issue. The lack of formatting to the Crucial M500 SSD seems to have been the root cause of the issue.
Appreciate your support!